1. Field of the Invention
The present invention relates to a thermoplastic resin composition comprising aggregated particles and a thermoplastic resin, a method for producing the thermoplastic resin composition, and a molded article obtained by melt-molding the thermoplastic resin composition.
2. Description of the Related Art
Thermoplastic reins can be recycled and applied to processing of melt-molding with high productivity (extrusion molding, injection molding, etc.), and thus useful as environmentally friendly and energy-sufficient materials. Above all, high-performance polymer materials (engineering materials) which can replace metals and ceramics have been used as constituent materials in various fields such as an electricity, electronics, mechanics, optical instruments, automobiles, aircraft, and medical fields.
Among thermoplastic resins, liquid crystal polymers provide molded articles which have excellent properties such as mechanical strength and heat resistance, and are thus useful particularly for constituent materials in a variety of fields. The liquid crystal polymers have rigid molecules, thus form polydomains in a liquid crystal state without entanglement even in a molten state, and behave with molecular chains substantially oriented in the flow direction due to shearing during molding, thereby allowing molded articles with excellent mechanical strength to be obtained.
Meanwhile, in the case of melt-molding a thermoplastic resin to obtain a molded article, a molding method referred to as injection molding is normally used when a molded article in a relatively complex shape is to be obtained. This injection molding is a method in which, with a mold having a void (cavity) corresponding to a desired shape for the molded article, a molten resin is injection molded into the cavity, the molten resin injected is further subjected to cooling solidification, followed by separation of the mold, thereby producing a molded article. In the production of a molded article through injection molding, when the molded article intended has a shape, for example, with a hollow portion, in the cavity, the molten resin injected may divide into multiple flow channels or the molten resin divided may further merge again. Then, the portion where the molten resin has merged may provide color unevenness or concave in a molded article to be obtained, resulting in a defect in appearance (defective appearance). This defective appearance of the molded article is normally referred to as a weld line.
In order to improve the defective appearance of the molded article, it is necessary to reduce generation of the weld line, and various ideas have been thus tried during melt-molding. For example, Japanese Patent Application Laid-Open No. 11-291277 discloses that the weld line can be reduced by providing a thick-walled portion around a through hole (hollow portion) in a molded article with the through hole formed in a plate-shaped main body portion. However, this consideration will limit the shape of the molded article, and may fail to conform to the intended use of the molded article.